7th Grade Math

R16 Selected Answers and Solutions

Selected Answers and Solutions

2929 a. Let n represent the percent of viewers

watching comedy, jokes, and bloopers.

52,540,000 = n · 142,000,000 Write the percent equation.

_142,000,00052,540,000 = 142,000,000__142,000,000n Divide each side by 142 million.

0.37 = n Simplify.

37% of viewers watch comedy, jokes, and bloopers.

b. Let n represent the percent of viewers watching

news stories.

44,020,000 = n · 142,000,000 Write the percent equation.

_142,000,00044,020,000 = 142,000,000__142,000,000n Divide each side by 142 million.

0.31 = n Simplify.

31% of viewers watch news stories.

c. Let n represent the percent of viewers watching

music videos and movie previews.

90,880,000 = n · 142,000,000 Write the percent equation.

_142,000,00090,880,000 = 142,000,000__142,000,000n Divide each side by 142 million.

0.64 = n Simplify.

64% of viewers watch music videos and movie

previews.

31. Sample answer: If the percent is less than 100%,
    then the part is less than the base; if the percent
    equals 100%, then the part equals the base; if the
    percent is greater than 100%, then the part is
    greater than the base. 33. B 35. D 37. 170.73


32. Soccer; 21 is 15% of 140
    Pages 342–343 Lesson 6-2D PSI


33. Find 10% of the number, then half of the 10%, and
    add together. 3. $3.50 5. 500; 60% · 830 ≈ 500


34. Sample answer: 2 quarters, 1 dime, 4 nickels,
    3 pennies
    99 25% off is one fourth less than the original
    price. $41 is close to $40. One fourth of $40 is $10.
    Taking $10 off the original price leaves us with $30
    as the sale price.


35. Sample answer: $120; $10 · 12 = $120


36. 15 · 18 + 18 · 20 = 630 ft^2. Then convert 630 ft^2
    to square yards. 630 ÷ (3 · 3) = 70 yd^2.
    Pages 348–350 Lesson 6-3B


37. -20%, decrease 3. 19%, increase 5a. about
    3.8%, increase 5b. about -2.9%, decrease 7. 40%,
    increase 9. -71%, decrease
    1111 The amount of change is $11.70 - $15.60 = -$3.90.
    Since the amount of change is negative, this is a
    decrease.
    percent of decrease = amount of decrease__original amount
    = _15.603.90 Substitution
    = 0.25 Simplify.
    = 25% Write 0.25 as a percent.
    There was a -25% percent of decrease.


38. -5%, decrease 15. 13%, increase 17. -38%,
    decrease 19. 2%, increase

2323 Write the percent of change equation. Substitute

the values you know, and solve to fi nd the original

amount. Let x = amount of change.

percent of change =

amount of change

__original amount

0.20 = __25,900,000,000x Substitute.

(25,900,000,000)(0.20) = 25,900,000,000x

Multiply each side by 25,900,000,000.

5,180,000,000 = x Simplify.

The amount of change was 5.18 billion.

Amount of change = new amount - original

amount

Let n = new amount.

5.18 billion = n - 25.9 billion Substitute.

5.18 billion + 25.9 billion = n Add 25.9 billion to each side.

31.08 billion = n Simplify.

The projected sales are $31.08 billion or about

$31 billion.

25. $60 sound system; 10 is a greater part
    of 60 than of 90. 27. Sample answer: Compare the
    original amounts. The ratio of the amount of
    change to a smaller original amount would be
    larger than the ratio of the same amount of change
    to a larger original amount. 29. 6,500 comments


26. 200 33. 0.3w = 17; 56.7 35. p = 0.64 · 150; 96


27. 5 = 0.2 · w; 25 39. Sample answer: 1.5 = n · 24;
    6.25%
    Pages 353–354 Lesson 6-3C


28. $3.10 3. $32.20 5. $37.73
    77 $1,500 computer, 7% tax
    100% + 7% = 107% Add the percent of tax to 100%.
    The total cost is 107% of the regular price.
    107% of $1,500 = 1.07 × 1500 Write 107% as a decimal.
    = $1,605 Multiply.
    The total cost of the computer is $1,605.


29. $14.95 11. $7.99 13. $96.26 15. Yes; Sample
    answer: $84 was earned.
    1717 Combine the tax and the tip before calculating
    the total price: 0.0625 + 0.20 = 0.2625. Multiply the
    tax and tip by the price of the bill to fi nd the tax
    and tip: $28.35 × 0.2625 = $7.44. Add tax and tip to
    bill. $28.35 + $7.44 = $35.79


30. $134.82 21. $54, $64.80; The percent gratuity is
    20%. All of the other pairs have a gratuity of 15%.


31. B 25. 50%, increase 27. 73%, increase 29. _ 358


32. _ 449
    Pages 357–358 Lesson 6-3D


33. $157.50 3. $1,395.65 5. $98.90 7. $1,080.00


34. $4.90
    1111 First, fi nd the amount of the discount.
    20% of $7.50 = 0.20 · 7.50 Write 20% as a decimal.
    = $1.50 The discount is $1.50.

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